Geology and Uranium Deposits of the Gochetopa and Marshall Pass Districts, Saguache and Gunnison Counties, Colorado U.S. GEOLOGICAL SURVEY PRO FESS I 6N A L P A PE R 1457 AVAILABILITY OF BOOKS AND MAPS OF THE U.S. GEOLOGICAL SURVEY Instructions on ordering publications of the U.S. Geological Survey, along with prices of the last offerings, are given in the cur­ rent-year issues of the monthly catalog "New Publications of the U.S. Geological Survey." Prices of available U.S. Geological Sur­ vey publications released prior to the current year are listed in the most recent annual "Price and Availability List" Publications that are listed in various U.S. Geological Survey catalogs (see back inside cover) but not listed in the most recent annual "Price and Availability List" are no longer available. 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E-146, 701 C St. Maps For maps, address mail orders to U.S. Geological Survey, Map Distribution Maps Federal Center, Box 25286 Maps may be purchased over the counter at the U.S. Geologi­ Denver, CO 80225 cal Survey offices where books are sold (all addresses in above list) and at the following Geological Survey offices: Residents of Alaska may order maps from ROLLA, Missouri-1400 Independence Rd. Alaska Distribution Section, U.S. Geological Survey, DENVER, Colorado-Map Distribution, Bldg. 810, Federal New Federal Building - Box 12 Center 101 Twelfth Ave., Fairbanks, AK 99701 FAIRBANKS, Alaska-New Federal Bldg., 101 Twelfth Ave. Geology and Uranium Deposits of the Cochetopa and Marshall Pass Districts, Saguache and Gunnison Counties, Colorado By JERRY C. OLSON U.S. GEOLOGICAL SURVEY PROFESSIONAL PAPER 1457 A study of regional geologic history of two districts in which uranium deposits are related to fault zones, early Tertiary erosion surfaces, and volcanic rocks UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON: 1988 DEPARTMENT OF THE INTERIOR DONALD PAUL HODEL, Secretary U.S. GEOLOGICAL SURVEY Dallas L. Peck, Director Library of Congress Cataloging-in-Publication Data Olson, Jerry Chipman, 1917- Geology and uranium deposits of the Cochetopa and Marshall Pass districts, Saguache and Gunnison Counties, Colorado. (U.S. Geological Survey professional paper ; 1457) Bibliography; p. Supt. of Docs, no.: I 19.16:1457 1. Geology Colorado Saguache County. 2. Geology Colorado Gunnison County. 3. Uranium ores Colorado Saguache County. 4. Uranium ores Colorado Gunnison County. I. Title, II. Series: Geological Survey professional paper ; 1457. QE92.S24047 1988 557.88'49 86-600337 For sale by the Books and Open-File Reports Section, U.S. Geological Survey, Federal Center, Box 25425, Denver, CO 80225 Any use of trade names in this publication is for descriptive purposes only and does not imply endorsement by the U.S. Geological Survey. CONTENTS Page Abstract ........................... 1 Marshall Pass district ........................... 24 Introduction ....................... 2 Geologic setting ............................. 24 Previous work ................... 2 Proterozoic rocks ......................... 25 Uranium production ............. 3 Paleozoic rocks .......................... 28 Regional geology .................... 3 Cochetopa district ................... 6 Tertiary volcanic and intrusive rocks ........ 30 Geologic setting ................. 6 Faults .................................. 32 Proterozoic rocks ............. 6 Paleotopography and paleodrainage ............ 33 Mesozoic rocks .............. 7 Uranium deposits ............................ 33 Tertiary volcanic rocks ........ 10 Pitch mine .............................. 34 Faults ...................... 12 Uranium in Precambrian rocks ............. 35 Paleotopography and paleodrainage 12 Uranium and other mineral deposits 13 Uranium in the Harding Quartzite .......... 38 Los Ochos mine .............. 13 Source and localization of the uranium deposits . 40 Other mines and prospects 19 Application of genetic model to uranium exploration . 41 Source and localization of the uranium deposits 23 References cited ................................ 42 ILLUSTRATIONS Page FIGURES 1-5. Maps showing: 1. Location of Cochetopa and Marshall Pass districts, Colorado ................................... 2 2. Generalized geology of region including the Cochetopa and Marshall Pass districts, Colorado ....... 4 3. Generalized geology of the Cochetopa district, Saguache and Gunnison Counties, Colorado ......... 8 4. Paleotopographic contours on base of Oligocene volcanic rocks in parts of Gunnison and Saguache Counties, Colorado ............................................................................ 13 5. Paleotopographic contours and inferred paleodrainage on base of Oligocene volcanic rocks in the Cochetopa district, Saguache and Gunnison Counties, Colorado ....................................... 14 6. North-south section along bottom of ancestral Cochetopa valley, showing projection of modern Cochetopa Creek 15 7. West-east section along Los Ochos fault, showing geology of north wall of fault .......................... 15 8. Photograph of canyon of Cochetopa Creek, just south of Los Ochos mine ................................ 16 9. Diagram showing plan of main level and longitudinal projection of the main Los Ochos mine ............... 17 10. Photograph of Los Ochos fault, portal of West drift, Los Ochos mine ................................... 18 11. Generalized cross section of Los Ochos fault, Los Ochos mine .......................................... 18 12. Geologic map of an area near Cochetopa Creek, showing location of uranium, thorium, and mercury prospect pits 20 13. Generalized geologic map and cross section of the Marshall Pass district ................................. 26 14. Columnar stratigraphic section, Marshall Pass district ................................................ 28 15-19. Maps showing: 15. Inferred structure contours on base of Harding Quartzite, Marshall Pass district ................. 34 16. Inferred structure contours on base of Harding Quartzite, if present surface is tilted 7 ° toward N. 22 °30' E 35 17. Inferred structure contours on base of Tertiary volcanic rocks and gravels, Marshall Pass district ... 36 18. Inferred structure contours on base of Tertiary volcanic rocks and gravels, if present surface is tilted 7° toward N. 22°30'E ................................................................... 37 19. Region encompassing the Marshall Pass district and the western part of the Pueblo 1 ° X 2 ° quadrangle, showing localities prospected for uranium in Harding Quartzite and outcrop areas of lower Paleozoic sedimentary rocks .................................................................... 39 20. Projection showing three exposures of Tertiary volcanic rocks in relation to the Pitch mine ................. 41 in IV CONTENTS TABLES TABLE 1. Uranium production of the Cochetopa and Marshall Pass districts, 1956-1963, by mine ........................ 3 2. Correlation of Tertiary volcanic rocks in the Cochetopa district ............................................. 11 3. RaeU, thorium, and potassium contents of samples from the Los Ochos mine ................................. 19 METRIC CONVERSION FACTORS Metric unit Inch-pound equivalent millimeter (mm) = 0.04 inch (in.) centimeter (cm) = 0.39 inch (in.) meter (m) = 3.28 feet (ft) kilometer (km) =